let _Vue = null;

export default class VueRouter {
  static install(Vue) {
    // 判断当前插件是否被安装
    if (VueRouter.install.installed) return;
    VueRouter.install.installed = true;
    // 把VUe构造函数记录到全局变量
    _Vue = Vue;
    // 把创建Vue实例时候传入的router对象注册到Vue实例上

    // 混入
    _Vue.mixin({
      beforeCreate() {
        if (this.$options.router) {
          _Vue.prototype.$router = this.$options.router;
          this.$options.router.init();
        }
      },
    });
  }

  constructor(options) {
    this.options = options;
    this.routeMap = {}; 
    this.data = _Vue.observable({
      current: "/",
    });
  }

  init() {
    this.createRouteMap();
    this.initComponents(_Vue);
    this.initEvent();
  }

  createRouteMap() {
    // 遍历所有的路由规则，把路由规则解析成键值对形式，存储到routerMap中
    this.options.routes.forEach(route => {
      this.routeMap[route.path] = route.component;
    });
  }

  initComponents(Vue) {
    Vue.component("router-link", {
      props: {
        to: String,
      },
      render(h) {
        return h(
          "a",
          {
            attrs: {
              href: '#' + this.to,
            },
          },
          
          [this.$slots.default]
        );
      },
    });

    const self = this;
    Vue.component("router-view", {
      render(h) {
        const component = self.routeMap[self.data.current];
        return h(component);
      },
    });
  }

  initEvent () {
    window.addEventListener('hashchange', () => {
      this.data.current = window.location.hash.slice(1);
    });
  }
}
